1. Field of the Invention
The present invention relates to a tool controlling apparatus and, more particularly, a tool controlling apparatus for executing appropriately position control and torque control of a tool acting on a work. Further, more particularly, the present invention relates to a tool controlling apparatus which can provide a high precision work with high circularity not to disturb the diameter expansion of the work during rolling process as forming process of the work.
2. Description of the Related Art
The annular body forming apparatus which is one of tool controlling apparatuses in the related art has been disclosed in Japanese Patent Examined Publication (KOKOKU) Hei 3-31534. In this apparatus, the work is sandwiched between a forming roller and a mandrel, the forming roller is rotated upon an axis which is parallel with the mandrel, and a diameter of the work is expanded by pushing the forming roller relatively against the work to roll the work while rotating the work. At this time, guide rails, etc. support the work as the annular body during the rolling process to keep circularity of the work. An outer diameter detecting lever which contacts an outer peripheral surface of the work and a sensor for detecting a displacement amount of the outer diameter detecting lever are provided. The outer diameter of the work can be detected by the outer diameter detecting lever and the sensor during the process.
FIG. 19 is a sectional view showing the rolling situation of the annular body forming apparatus in the related art. In the rolling process by the annular body forming method in the related art, contact between a work 305 and a forming roller 315 is changed from point contact to surface contact by bringing the forming roller 315 close to the work 305 relatively in the initial feed. After the forming roller 315 has come into surface contact with the work 305, the forming roller 315 and a mandrel 304 are then brought close to each other at a predetermined quick feed in the rough feed. Thus, the work 305 is rolled by a large torque, a diameter expanding speed of the work 305 is accelerated, and the torque in the rough feed has a maximum value during the rolling process.
At this time, a pair of guide rollers 306 are employed to support an outer surface of the work 305 while fixing position of the work 305. If a work holding force by the guide rollers 306 is insufficient at this point of time, abnormal vibration is easily generated in a work rolling portion. In addition, because polygonal components are generated once the vibration is generated, it is impossible to form the round work, so that the outer diameter of the work 305 becomes uneven.
Then, when the outer diameter of the work 305 reaches a diameter to be switched to the finishing feed, a relative moving speed between the mandrel 304 and the forming roller 315 is reduced to improve the circularity of the work 305 by reducing a cutting push-down amount mm/rev (one revolution) (referred to as a "draft amount" hereinafter), and then the process is shifted to the finishing feed. When it is detected that a torque in the finishing feed become a steady state and then the outer diameter of the work 305 comes up to a predetermined dimension, the rolling process is terminated.
Normally, if the torque of the guide rollers 306 is set small in the finishing feed rather than the rough feed, the diameter expansion of the work is not disturbed and thus the good working can be attained. In this manner, such a problem has existed that the stable working conditions cannot be achieved since the torque is changed largely during the rolling process. In particular, as for the hydraulic guide rollers in the related art, it has not been apparent how the pushing force against the work should be changed in respective steps of the rolling process. Therefore, it is continued to apply a constant pushing force to the work from a run-in period of the initial rolling (initial feed) to the end of the finishing feed. Particularly, if the work is guided in the finishing feed stage by the same pushing force against the work as in the rough feed stage, it is possible to spoil the circularity of the work 305. Especially, if the thin work is to be rolled, the above event which is the influence of the pushing force of the guide rollers 306 applied to the work 305 becomes prominent. In addition, because of cycle shortening, it is desired that, in respective stages from the end of the finishing feed to the release of the guide rollers 306, the guide rollers 306 must return quickly to the home position to start the next working. In this manner, according to the annular body forming apparatus in the related art, it has been difficult to attain both the improvement in working efficiency and the improvement in working precision simultaneously.
A mechanism of the guide rollers 306 is constructed such that the guide rollers 306 are fitted on both upstream and downstream sides of the position, at which the work 305 is put between the mandrel 304 and the forming roller 315 to accept the plastic working, so as to sandwich the work 305, then apply the constant force to the work 305, and then are moved back by a force generated when the diameter of the work 305 is expanded by the rolling process. In this case, the work 305 is swung to one side when one of a pair of guide rollers 306 pushes the work 305, and the other of a pair of guide rollers 306 receives such swing force at that time to absorb the swing of the work 305. This phenomenon is repeated like a so-called resonance phenomenon, so that it is difficult to stabilize the position of the work 305. Therefore, respective guide rollers must be synchronized forcibly to be opened/closed simultaneously, otherwise a one-way clutch which is set free in the direction along which the work is excessively pushed to prevent the excessive pushing of the work 305, etc. must be incorporated. In particular, if such resonance phenomenon cannot be prevented in the finishing stage, the circularity of the work 305 is degraded extremely.
In order to improve a precision of the circularity of the work, the draft amount must be reduced by setting the finishing feed employed to roll the work 305 at a low speed. At this time, unless reduction of the draft amount is carried out so as to avoid the above resonance phenomenon, the work with good thickness deviation and circularity cannot be obtained. As the result of many experiments of the rolling process, it has been found that a relationship between pushing forces of the upstream and downstream guide rollers 306 in the finishing feed has an effect on the precision of the circularity. In other words, it has been found that it is preferable that the pushing force of the guide roller applied to the work should be made small in the finishing feed rather than the rough feed, or it is important that the pushing force of the downstream guide roller is set stronger to support the work 305 than the upstream guide roller. In addition, if the small pushing forces rather than those in the rough feed are applied from both upstream and downstream guide rollers in the finishing feed, or if the strong pushing force is applied to the work by the upstream guide roller 306 when the plastic working of the work 305 is executed in the finishing feed, the circularity is deteriorated. Therefore, the upstream guide roller must be positioned away from the work 305.
When the work is rolled by increasing the draft amount since at first the work has wrong profiles of work material such as the thickness deviation, the circularity, etc., the resonance phenomenon appears apparently. Therefore, in order to prevent the resonance phenomenon, a function of strongly pushing the work by the guide rollers 306 from both the upstream and downstream sides (up to the rough feed) must be applied.
However, when the process is shifted to the finishing feed, the thickness deviation and the circularity are gradually corrected and thus the resonance phenomenon caused between the work and the guide rollers is reduced rather than the rough feed, so that the position of the work can be stabilized. FIG. 18 is a side view showing the situation of the work which is subjected to the rolling working between a forming roller and a mandrel. As shown in FIG. 18, a thickness t0 of the work prior to the rolling process is larger than a thickness ta of the work after the rolling process and an inlet velocity v1 of the work prior to the rolling process is smaller than an outlet velocity v0 of the work after the rolling process, and also the direction of the velocity is abruptly changed. Furthermore, since the work has the thickness deviation in the rough feed of the mandrel, or since the draft amount per revolution of the mandrel against the work is selected largely, the downstream rolling portion is pushed out strongly unless the guide rollers are provided, so that the position of the work becomes unstable to thus cause the vibration. If the pushing forces of the upstream and downstream guide rollers become uneven or are reduced small at the time of such unstable state, the resonance of the work is caused up and down vertically on the basis of a shaft center X--X connecting a center of the mandrel and a center of the forming roller. Unless such vibration is stopped, not only the rolling process of the work becomes difficult due to the vibration but also the thickness deviation and the circularity of the work are not corrected or sometimes they become worse, and further the damage of the die is caused.